As in the previous year, the ongoing objective of this proposal is to utilize monoclonal antibodies to study the mechanism of JHM virus (JHMV) induced demyelination in experimental infections of mice. This animal model has many similarities to the human disease multiple sclerosis. During the next year, the following experiments will be performed. Further antigenic variant viruses will be generated. The variants will be used to map the structure of epitopes on the E2 protein of JHMV. The variants will also be use in detailed pathogenesis experiments. Double variants with two point mutations will also be generated and studied. The response of the immune system to the variants and the mechanisms underlying diminished neurovirulence will be explored. When the sequence of the gene for E2 becomes available, the location of variant mutations will be mapped. The tropism of variants in vitro organotypic cultures will be studied. Finally, attempts to produce antibody to the cellular receptor for JHMV will be undertaken, either by use of anti-idiotypic antibodies or immunization with receptor-positive cells. The use of rat-mouse monoclonal antibodies, as well as mouse-mouse monoclonal antibodies, will be explored when seeking anti-receptor antibodies.